We went out along with the Messenger of Allah ﷺ for some battle in intense heat, so much so that one of us placed his hand on his head, or placed his palm on his head, due to intense heat, No one of us fasted except the Messenger of Allah ﷺ and 'Abd Allah b. Rawahah.  

خَرَجْنَا مَعَ رَسُولِ اللَّهِ ﷺ فِي بَعْضِ غَزَوَاتِهِ فِي حَرٍّ شَدِيدٍ حَتَّى إِنَّ أَحَدَنَا لَيَضَعُ يَدَهُ عَلَى رَأْسِهِ أَوْ كَفَّهُ عَلَى رَأْسِهِ مِنْ شِدَّةِ الْحَرِّ مَا فِينَا صَائِمٌ إِلاَّ رَسُولُ اللَّهِ ﷺ وَعَبْدُ اللَّهِ بْنُ رَوَاحَةَ  

The Messenger of Allah ﷺ said: If anyone has a riding beast which carries him to where he can get sufficient food, he should keep the fast of Ramadan wherever he is when it comes.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ كَانَتْ لَهُ حَمُولَةٌ تَأْوِي إِلَى شِبَعٍ فَلْيَصُمْ رَمَضَانَ حَيْثُ أَدْرَكَهُ  

The Messenger of Allah ﷺ as saying: If anyone is on a journey and Ramadan comes... He then narrated the rest of the tradition to the same effect.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ أَدْرَكَهُ رَمَضَانُ فِي السَّفَرِ فَذَكَرَ مَعْنَاهُ